The Importance Of The Standing Reflux Ultrasound & Why You Should Insist On One

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Chronic venous insufficiency (CVI) affects 25% to 90% of the population in their lifetime and is the underlying cause of symptoms such as leg heaviness & fatigue, ankle swelling, restless legs, night cramps/Charley horses, spider and varicose veins, skin discoloration, and venous ulcers. In most cases, a thorough history and physical exam can make the diagnosis of CVI. However, objective evidence is required to support this diagnosis to ensure that the proper treatment is recommended and to meet insurance company requirements for payment. This objective evidence is provided by the standing reflux ultrasound (SRU). Unfortunately, the SRU is often done incorrectly – even by venous experts – leading to misdiagnosis and unnecessary procedures.

Fig 1. Incompetent Valves
What causes CVI?

CVI is caused by malfunctioning valves within the leg veins. Normally, these valves open and close (first two images in Fig. 1) to push blood one-way towards the heart. When the valves close, blood is prevented from going backwards (or refluxing) towards the floor. Valves that are malfunctioning are referred to as incompetent. Incompetent valves (3rd image in Fig. 1) do not open and close but rather stay in the open position. If one is standing and has incompetent valves, blood goes backwards (or refluxes) down the leg towards the floor due to gravity. This results in blood pooling in the calf and ankles and leads to leg heaviness, fatigue, ankle swelling, varicose veins, etc.

What does a SRU measure?

The SRU measures the rate at which blood refluxes towards the floor. This rate is referred to as the Reflux Time (RT). A RT greater than 0.5 seconds (or 500 milliseconds) is considered CLINICALLY SIGNIFICANT. However, whether treatment is needed or not depends on 4 factors:

  • Is the RT > 0.5 seconds in the superficial vein?
  • Is the the vein at least 5.0-5.5 mm in diameter?
  • Is there significant reflux at the junction of the superficial vein with the deep vein?
  • Does the patient have significant symptoms of CVI?
Fig 2. Significant reflux of 4562 milliseconds in the Great Saphenous Vein (GSV) that measures 3.69 mm in diameter

It is possible to have significant reflux on the SRU and NOT have symptoms at all. In such cases, no treatment is needed and patients should be educated about what to look for should CVI symptoms develop down the road.

It is possible to have significant reflux on the SRU and NOT have symptoms at all.

How is a SRU performed?

While there may be some variation in how the SRU is performed, I will describe how it is performed in my practice. The SRU evaluates both deep AND the superficial veins of the leg. The deep veins are evaluated for deep vein thrombosis (DVT) and reflux. The superficial veins are also for reflux as well as clot, referred to as superficial thrombophlebitis which is different than DVT. It is important to evaluate both the deep and superficial veins for reflux as this information can alert the physician to more complex vascular conditions.

During the SRU, the patient is often evaluated first for DVT while laying flat (supine). This part of the exam can take 15-20 min for both legs. In the second part of the exam (which can take ~ 40 minutes), the veins are examined for reflux. It is OK to start with the patient flat if it is easier for the technologist but the patient MUST be stood up if reflux is not seen in the supine position. The technologist will squeeze the calf to augment blood flow (or push the blood up towards the heart) or even better, use an inflatable cuff on the leg to assist with augmentation. If the vein valves are working properly, squeezing the calf will augment the blood towards the heart but no blood will reflux towards the feet. If the valves are incompetent, then the blood will go up towards the heart for a bit and then reflux. The technologist will measure the RT. If there is no reflux seen or if the RT is less than 0.5 seconds, then the patient MUST be stood up to see if reflux occurs by introducing gravity into the examination. After all, it is when we are standing on our feet that we experience CVI symptoms, not when we are laying down.

If there is no reflux seen or if the RT is less than 0.5 seconds, then the patient MUST be stood up to see if reflux occurs by introducing gravity into the examination.

Fig 3. SRU performed with a cuff on the calf for more reliable augmentation
How does an improperly done ultrasound lead to the wrong treatment?

The SRU is important not only to properly diagnose CVI but also to prevent the physician from providing the wrong treatment. Other vascular conditions such as May Thurner Syndrome (MTS) are increasingly being diagnosed in many patients when in fact CVI is statistically much more common than MTS. This has led to many patients unnecessarily receiving a permanent metal stent when in fact no such stent is needed if the proper diagnosis is made.

A common scenario that I see in my practice is that of a woman in her late 30’s with 2-3 kids. She has noticed over the past few years that her legs are increasingly feeling heavy and fatigued. She is on her feet or sitting at a desk all day with her legs in the dependent position and by the end of the day, her ankles are swollen. All she wants to do when she gets home is sit with her legs elevated, but she is unable to as she has young children at home. At night, she has severe restless legs and gets painful Charley horses in her thigh and calf and she jumps out of bed. She has been wearing compression stockings which helped for a couple years and now her symptoms are worsening.

In many practices, this patient will undergo an ultrasound in the supine position to look for reflux but none will be found. Due to the presence of calf or ankle swelling, a CT/MR will be obtained that shows compression of the left common iliac vein, confirming the diagnosis of MTS. This is a wrong assumption in my opinion (read “Secret Revealed: The % of Iliac Vein Compression Needed To Justify A Stent“). A catheter venogram with intravascular ultrasound (IVUS) is performed confirming the presence of compression and a stent is placed. Months later, the patient continues to have the same if not slightly worsened symptoms. During a follow-up visit with her physician, the patient is told that nothing more can be done.

When such a patient presents for a second opinion, the first thing I ask them after a thorough history and physical exam is whether an SRU was done. Nine out of ten times the patient will say no. We will then perform a SRU, find significant reflux, and then successfully treat the patient for CVI — the condition that was not properly diagnosed the first time. Unfortunately, the patient now has an unnecessary permanent stent that cannot be removed.

Why is the SRU not routinely done?

There are several reasons as to why the SRU is not routinely done. First is education. Many physicians who treat venous disease are unaware of the underlying pathophysiology of venous disease. This lack of awareness leads to an improper history and physical exam which if done properly clinches the diagnosis of CVI in most cases even before any imaging is done.

Secondly, performing a SRU is very difficult from a physical standpoint for the technologist. It is hard on the technologist’s back, shoulders, and neck to constantly bend down and scan legs for several hours a day. Even after 20 yrs of treating vascular disease, I have yet to find an US technologist that enjoys doing these exams. Fortunately, providing a raised platform on which the patient can stand for the SRU makes a world of difference for the technologist (see Fig 3) as they can sit comfortably and perform an SRU without putting their bodies at risk of injury.

Third, the SRU can be very difficult for a patient to tolerate. While initially the SRU doesn’t seem difficult, standing for nearly an hour in one position can be extremely challenging for many patients. It’s not uncommon for patients to feel dizzy or faint during this exam. It’s ok to tell the technologist that a break is needed. If a patient cannot stand, then at the very least the head of the table or stretcher should be raised (reverse Trendelenburg position) so that the legs are in the dependent position (Fig. 4).

Fig 4. If patient is unable to stand, reverse Trendelenburg position can be used.

Finally, there is cost. Insurance companies do not understand the importance of the SRU and what is involved in performing one. The reimbursement for the SRU which can often take over 1 hour to perform is THE SAME as the 15-20 minute ultrasound that is done to evaluate for DVT. No wonder no one wants to do the SRU!

The SRU provides a lot of information to the physician who has a deep understanding of all aspects of venous disease. The information from the SRU should be combined with the patient’s history and physical exam to lead the physician and patient down the correct treatment pathway.

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